Cannabis

Lecture 10: Delta Nine Tetrahydrocannabinol (THC)

Overview of THC and Cannabinoids

  • THC (delta nine tetrahydrocannabinol) is the psychoactive compound in the cannabis plant.

  • Cannabis contains various unique compounds called cannabinoids, which include:

    • THC: Primary psychoactive compound.

    • CBD (cannabidiol): Not psychoactive, responsible for some medical benefits of cannabis.

Historical Context

Early Uses of Cannabis

  • Cannabis cultivated for over 10,000 years; initially used primarily for fiber, not psychoactive effects.

  • Oldest cultivated plant not used for food.

  • Evidence of psychoactive use around 3,000 BC (rounded from 2,800 BC).

Introduction to North America

  • Introduced in early 1600s to Canada and the U.S. for fiber use (e.g., rope, clothing) rather than recreational purposes.

Spread in Europe

  • Early to mid-1800s: French troops exposed to cannabis in North Africa (Napoleon's campaigns).

  • The practice of consuming cannabis, known as Dala Mask, became popular among artists and writers.

    • Dala Mask created by boiling cannabis in butter to extract THC, flavored with pistachio or cinnamon.

Patent Medicines in the Late 1800s

  • Cannabis featured in patent medicines, often combined with alcohol, claiming therapeutic effects.

  • Notable product: Tilden's Extract of Cannabis Indica.

  • Other substances included cocaine and opiates.

Prohibition Era (1919 - 1933)

  • Alcohol prohibition led to increased marijuana use in tea rooms as it was not illegal.

  • Transition from alcohol to cannabis during this period, responding to laws on alcohol consumption.

  • Rise of campaigns led by figures like Harry Anslinger against drug use, often racially charged.

    • Marijuana laws associated with ethnic minority use, targeting groups such as African Americans and Mexicans.

Current Use of Cannabis in Canada

  • Approximately 25% of Canadians aged 16 or older reported cannabis use in the last year, with higher prevalence among younger demographics (ages 18-24).

  • Potential increase in usage following the decriminalization of marijuana products.

  • 25% of users report consumption at least five times a week.

Chemical Composition and Effects of Cannabis

THC Isolation

  • THC was isolated in 1964, later than similar psychoactive substances (e.g., cocaine and morphine in the 1800s).

Methods of Cannabis Consumption

  1. Marijuana: Dried leaves and flower buds, containing approximately 2% THC in the 1970s, now up to 35% or more.

  2. Hashish: Concentrated form made from trichomes, with THC concentrations around 40%.

  3. Hash Oil and Resins: Further refined products, often over 67% THC.

    • Dabbing technique using heated surfaces for vaporization.

Administration Routes

  • Smoking: Most common method using joints or bongs, with deeper inhalation and longer holding of smoke.

  • Oral Consumption: Slower onset, requires larger doses for effects; eating delays peak effects.

    • Duration: Inhaled effects last 2-4 hours, peak at 30 minutes; oral methods take longer to peak.

    • Elimination Half-Life: About 5 days, suggesting a drug-free status requires approximately 30 days without consumption.

Effects of THC

Dose Dependency

  • Low doses may lead to euphoria and relaxation, while higher doses can cause hallucinations, delusions, and body image distortions.

Sexual Performance Effects

  • THC at low doses may increase libido via testosterone rise; at higher doses, decreases sexual performance in both genders (similar to alcohol effects).

Physiological Effects

  • Common effects: Drooping eyelids (due to muscle tone neurotransmitter), dry mouth (anticholinergic effect), increased hunger (activates hunger systems).

    • THC impairs learning and memory, particularly affecting the cholinergic systems involved.

Expectancies and Perceptions

  • Expectancies can affect reported sensations and behaviors associated with cannabis, demonstrated in controlled studies (e.g., balanced placebo design).

Medical Benefits of Cannabis

  • Suggested for conditions like chronic pain, but benefits largely attributed to CBD rather than THC.

  • Synthetic alternatives (e.g., Marinol and Sativex) used for medicinal purposes without psychoactive effects.

Concerns About Cannabis Smoking and Health Risks

Lung Health

  • Research indicates marijuana smoke has higher harmful substances than tobacco smoke.

  • A comparison showed significant tar staining from marijuana compared to tobacco, suggesting greater lung damage risk.

  • Factors include:

    • Lack of filters on joints.

    • Smoking techniques that increase inhalation depth and duration.

Driving Impairment

  • THC negatively impacts reaction times and driving abilities similar to alcohol, often considered more impairing.

  • Secondhand exposure to THC in social settings poses additional risks.

Cognitive and Memory Effects

Working Memory Impairment

  • THC impacts short-term/working memory, requiring further investigation into chronic use effects on cognitive ability.

  • Animal studies (e.g., radial maze) show THC impairs ability to remember which paths yield rewards.

Human Studies and Long-term Effects

  • Delayed matching to sample tasks reveal acute impairment of learning and memory under THC influence.

  • Longitudinal studies hint at cognitive issues, especially with early onset of use.

  • Cross-sectional study approach suggests heavy users show significant deficits in cognitive function compared to non-users.

Conclusion of Lecture

  • THC demonstrates profound effects on cognitive skills, memory, driving ability, and overall health considerations. Future discussions will address neurochemical effects and further implications of THC consumption.